Mechanism of Single Proppant Pressure Embedded in Coal Seam Fracture

Abstract

The strength and rigidity of proppant and coal are quite different. Proppant is easily embedded in coal, resulting in the decrease of fracture aperture and conductivity. The mechanism of proppant embedded in the coal fracture surface needs further study. In this paper, through theoretical analysis and experimental research of single proppant embedded, the proppant embedded law is analyzed from macro and micro aspects. The damage factor of coal surface is introduced, the damage model of the whole process of single proppant pressure embedded is established, and the mechanism of coal fracture surface embedded pit and cracks is revealed. The results show that, from the center of the contact surface to the outside, the surface failure forms of coal fracture are pressure failure, tensile-shear failure, and tensile failure. The proppant is embedded in the coal fracture surface to form four areas: central compaction area, layered fracture area, fracture development area, and original state area. During the energy release of proppant embedded in coal, the energy of proppant is released first and the energy of coal is released later. Greater than 3 times the contact radius, the influence of single proppant on the coal fracture surface can be ignored.

Fracturing Construction Curves and Fracture Geometries of Coals in the Southern Qinshui Basin, China: Implication for Coalbed Methane Productivity

“…To prevent the closure of a hydraulic fracturing-induced fracture network under in situ stress, proppant injection is commonly employed to maintain the fracture open. − Insufficient hydraulic fracture (HF) support length is one of the main reasons for the low production of CBM wells . The proppant migration efficiency depends on many factors such as injection rate, proppant specification, fluid viscosity, fracture width, and roughness. − For a complex fracture network composed of multilevel fractures, the migration efficiency of the proppant also depends on the number of secondary fractures and their angles with the main fractures.…”

Migration and Distribution Characteristics of Proppant at the Corner of Horizontal Fracture Network in Coal Seam

“…In order to improve the exploitation efficiency of coalbed methane, hydraulic fracturing (Huang et al, 2011;Lv et al, 2012), CO 2 phase change fracturing (Colmenares and Zoback, 2007;Xu et al, 2017), nitrogen fracturing (Cai et al, 2015;Qin et al, 2017), and other methods are often used to transform the coal seam, activate the internal bedding and cleat of the coal seam, and form a complex fracture network system penetrating each other. The key of fracturing technology is to form fractures with high conductivity (Li et al, 2021). However, under the action of closure stress, the coal seam fracture is easy to close.…”